Mechanism of Hydrolysis of the Treated Sago Starch Granules by Raw Starch Digesting Amylase from Penicillium brunneum

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Abstract
We have prepared raw starch digesting amylase from Penicillium brunneum, which is similar to other raw starch digesting enzymes, and is effective in hydrolyzing raw cereal starches, but not effective for raw sago starch and raw root starches. Treatment of sago starch granules before incubation with the enzyme by heating to below gelatinization temperature at low pH condition was effective in improving the hydrolysis. Observation by scanning electron microscope showed that structure of treated sago starch granules at 60°C pH 2.0 for 2h was not changed. Observation under polarized light showed the birefringence clearly was preserved. However, viscosity of treated sago starch granules decreased. After incubation with the enzyme, untreated starch granules corroded and several holes were seen on the surface of granule. Enzyme action on the treated starch granules resulted in much higher intensity of degradation and the holes deepened into the interior of granules. Analysis of the product of this process showed that mainly glucose was produced from the hydrolysis of treated or untreated sago starch granules by crude enzyme. But on gelatinized sago starch other types of sugars were formed during enzyme reaction.